Experimental study on shear strengthening of reinforced concrete beams using ultra-high performance fiber reinforced concrete

This study investigates the effectiveness of using ultra-high performance fiber reinforced concrete (UHPFRC) to strengthen RC beams and improve their shear strength. Thirteen RC beams were cast and tested up to failure using a four-point loading test. One beam was kept as a control beam without strengthening, and the other twelve beams were strengthened by various strengthening schemes. The following key parameters were investigated: the number of strengthening sides, the thickness of the UHPFRC layer, the reinforcement of the strengthening layer (type of steel mesh, inclined stirrups, and without any reinforcement), and the volume fraction of steel fibers. The test results demonstrate that using the UHPFRC strengthening technique provides an efficient method for improving R.C. shear performance. In comparison with the un-strengthened beam the shear strength and ductility of the strengthened beams with UHPFRC layers have increased by 91% and 56%, respectively. The behavior of the beams is improved by increasing strengthening sides. The beam with three strengthened sides has demonstrated the highest shear strength. It reached 65% increase in ultimate load, while strengthening on one side and two sides reached 41% and 56%, respectively, compared to control specimens. As expected, the results also revealed that using the strengthening layer with reinforcement provides better shear performance than using UHPFRC layers without reinforcement. It has also been found that inclined stirrups perform more effectively than steel mesh.